1. Field of the Invention
The present invention relates to the replacement of Refrigerant R-12 (dichlorodifluoromethane) with a blend refrigerant that is less damaging to the ozone layer in systems designed to use Refrigerant R-12 (dichlorodifluoromethane). More particularly, the present invention relates to an improved refrigerant composition, method and apparatus for refrigeration wherein two non-R-12 refrigerants are mixed in a defined ratio to balance the objectives of providing a temperature-pressure relationship of the mix approximating that of Refrigerant R-12 (dichlorodifluoromethane), while at the same time being less flammable than other replacement refrigerants, for HVAC, refrigeration and automotive applications. The mixture is compatible with Refrigerant R-12 (dichlorodifluoromethane) so that it can supplement and replace Refrigerant R-12 (dichlorodifluoromethane). A further particularity of the instant invention relates to an improved method and apparatus for refrigeration wherein refrigerant mixture is mixed with a lubricating oil compatible with the lubricating oil(s) placed in the equipment during manufacture or assembly.
2. General Background
R-12 refrigerant dichlorodifluoromethane (hereinafter sometimes called “Refrigerant R-12 (dichlorodifluoromethane)”) was once the major, if not sole refrigerant, used in residential air-conditioners, refrigerators, freezers and automobiles. Refrigerant R-12 (dichlorodifluoromethane) is also known as Freon 12 a trademark of E. I. du Pont de Nemours & Co. Inc. for dichlorodifluoromethane. Hereinafter, “Refrigerant R-12 (dichlorodifluoromethane)” is used in this specification to denote dichlorodifluoromethane, regardless of the source.
Refrigerant R-12 (dichlorodifluoromethane) came under attack both nationally and internationally as an ozone layer-damaging chemical with a high global warming factor. Both the national and international scientific communities linked Refrigerant R-12 (dichlorodifluoromethane) with damage to the earth's protective ozone layer. Air-conditioners, refrigerator/freezers and auto units containing R-12 are believed to be a global source of ozone-damaging material and a direct cause of global warming.
In response to scientific concern and a national and global outcry over the use of Refrigerant R-12 (dichlorodifluoromethane) in air-conditioning and refrigeration, the United States Congress acted to first reduce and then ban the use of Refrigerant R-12 (dichlorodifluoromethane) in units.
Prior to banning the sale of quantities of Refrigerant R-12 (dichlorodifluoromethane), owners of equipment with Refrigerant R-12 (dichlorodifluoromethane)-based air-conditioning units were able to purchase the level of refrigerant in their equipment with only the need of a refrigerants license as required by the Clean Air Act. Millions of units containing refrigerant R-12 (dichlorodifluoromethane) were sold in the United States prior to the start of mandatory phase out set forth by Congress and the international community.
Refrigerant R-12 (dichlorodifluoromethane) recharging typically involves 30 lb. cans or cylinders used in the HVAC/R and auto industry. The cylinders are fitted with a dispensing outlet compatible with a commercially available refrigeration manifold. In order to recharge an air-conditioning system, a customer need to only fit the can or cylinder to the manifold and discharge, or “add to” the refrigerant charge directly into the air conditioning system.
Following Congress's limitations on the sale of Refrigerant R-12 (dichlorodifluoromethane) millions of equipment owners with Refrigerant R-12 (dichlorodifluoromethane)-based air-conditioning units were left with no choice other than to reclaim or seek replacement refrigerants to service these units. Intentionally mixing of refrigerants is currently illegal by standards set forth by the Clean Air Act.
In response to Congress's ban on the use of Refrigerant R-12 (dichlorodifluoromethane) in air-conditioning, service dealers retrofitted existing Refrigerant R-12 (dichlorodifluoromethane)-based air-conditioning units with new, non-R-12 refrigerants.
Other refrigerants were developed to replace the prior, now banned R-12 refrigerant, or dichlorodifluoromethane. For example, Tamura et al. (U.S. Pat. No. 4,983,312) discloses a refrigerant consisting essentially of R134a (1,1,1,2-tetrafluoroethane) and R142b (chlorodifluoroethane). Tamura et al., however, makes no teaching or suggestion of a lubricant.
Wilczek (U.S. Pat. No. 5,384,057), Gorski (U.S. Pat. No. 4,971,712), and Anton of DuPont (U.S. Pat. No. 5,145,594) disclose other R-12 replacements in the form of a blend of certain synthetic lubricants in various R134a and R134a/R125 refrigerant systems. The DuPont patents discuss a gas known as R125 (pentafluoroethane). R125 is five fluorine atoms bonded to an ethane molecule. This is a very large molecule for a refrigerant. It is currently being produced for refrigeration only. Anton discloses the use of a lubricant comprising at least one cyanocarbon compound. Wilczek discloses a fluorosiloxane as a lubricant. Gorski discloses a polyakylene glycol as a lubricant.
Begeman, et al. (U.S. Pat. No. 3,092,981) disclose the use of a fluoro halo derivative of an aliphatic hydrocarbon as a refrigerant in combination with alkylbenzene of 1 to 50 carbons and a viscosity of 50 to 2000 SUS (Saybolt Universal Seconds) at 100° F. Olund (U.S. Pat. No. 3,642,634) discloses a lubricating oil for refrigeration equipment consisting essentially of a high viscosity alkylbenzene having a viscosity in the range of 3000 to 1,000,000 SUS at 100° F. and a refrigerant containing a halongenated alkyl working fluid and this high viscosity alkylbenzene. (U.S. Pat. No. 3,733,850 and U.S. Pat No. 4,046,533). Kaneko (U.S. Pat. No. 5,520,833) discloses the use of a lower viscosity (viscosity of 2 to 50 cst at 100° C.) alkylbenzene or alkylnapthelene with a substitute flon compound as a refrigerant. Generally, synthetic oils, such as alkylbenzene, and mineral oils have not been used in conjunction with R134a (1,1,1,2-tetrafluoroethane). As noted by Fukuda, et al (U.S. Pat. No. 5,417,872) R134a has unique properties due to its special chemical structure, so that it is not miscible in refrigerating machine oils used in the refrigeration systems of R-12 refrigerant, e.g. mineral oils (naphthenic oils, paraffinic oils) and synthetic oils such as alkylbenzene.
Systems that contain R-12 are still in use today. These older systems have common components: R-12, R-12 mineral oil lubricant, and water that is sequestered into the dryer. If R134a (1,1,1,2-tetrafluroethane) were added to the system, it would damage the system as follows: (1) if no lubricant is added to the R134a (as in U.S. Pat. No. 4,953,312 to Tamura et al.), then the R-12 system would be starved for lubricant, since the R134a gas is not miscible with the mineral oil lubricant; (2) if a synthetic lubricant is added to the R134a (as in Thomas et al., U.S. Pat. No. 5,254,280), then there is a different problem—that of moisture. Older systems can have water trapped in their dryers. Synthetic lubricants such as polyglycol or polysiloxane-based lubricants are hydrophilic. They are not only miscible with R-12 and R134a; they are also partially or completely miscible with water. Thus, if they are introduced into an R-12 system, they will pull this water out of the dryer into the refrigerant flow, possibly initiating corrosion and damage to pressure switches and the TX valve and possible other system components. This is why Elf Atochem and DuPont, to name a few publish elaborate flushing procedures and high efficiency dryer change-outs to prevent damage to the cooling system.
Weber (U.S. Pat. No. 5,492,643, U.S. Pat. No. 5,942,149, and U.S. Pat. No. 6,565,766) discloses yet another R-12 replacement consisting of a blend of R-142b (chlorodifluoroethane) in the amount of about 15% to about 40%, R-134a (tetrafluoroethane) in the amount of about 60% to about 85%, and a napthenic lubricating oil (Royco 783C, 783D). Weber generally teaches away from use of synthetic lubricants for the reasons mentioned above. Weber also teaches away from use of higher amounts of R-134a (tetrafluoroethane) noting that at higher temperature ranges, the pressure of R-134a in pure form is well above that of Freon 12 so that it would pose a hazard if used in equipment designed for using Freon 12. Further, Weber's replacement has the disadvantage of being relatively flammable because of its aerosoling tendency. In the Weber patents the preferred composition contains 79% R134a (tetrafluoroethane), 19% R142b (chlorodifluoroethane) and 2% (lubricant, Royco 783C or 783D) blend that is recognized by Refleak and Refprop (accepted industry computer modeling programs for fractionation analysis) to be flammable in the worst case formulation (WCF) temperature ranges of refrigeration uses as described in ASHRAE Standard 34 and accepted in industry. Proprietary computer modeling and bench top testing from DuPont and Honeywell also show flammability problems and concerns during worst-case fractionation (WCF) preventing acceptance in refrigeration applications. Thus, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. (ASHRAE) has been unwilling to grant a designation for Weber's refrigerant blend, in particular his preferred blend of 79%/19% and 2% lubricant. The focus of Weber's patents is directed to automobile applications, an industry that monitors less closely than the HVAC/R industry.
Thus, there exists a need for an R-12 refrigerant replacement having reduced flammability which meets ASHRAE's requirements for designation while at the same time providing lubrication.